San Antonio Mayor Julian Castro, left, and brother Joaquin Castro stand at the podium during preparations for the Democratic National Convention at Time Warner Cable Arena on September 2, 2012 in Charlotte, North Carolina. The DNC that will start on September 4 and run through September 7, will nominate U.S. President Barack Obama as the Democratic presidential candidate. less

San Antonio Mayor Julian Castro, left, and brother Joaquin Castro stand at the podium during preparations for the Democratic National Convention at Time Warner Cable Arena on September 2, 2012 in Charlotte, ... more

CHARLOTTE, NC - SEPTEMBER 02: San Antonio Mayor Julian Castro stands on stage during preparations for the Democratic National Convention at Time Warner Cable Arena on September 2, 2012 in Charlotte, North Carolina. The DNC that will start on September 4 and run through September 7, will nominate U.S. President Barack Obama as the Democratic presidential candidate. less

CHARLOTTE, NC - SEPTEMBER 02: San Antonio Mayor Julian Castro stands on stage during preparations for the Democratic National Convention at Time Warner Cable Arena on September 2, 2012 in Charlotte, North ... more

San Antonio Mayor Julian Castro, left, who will be the convention keynote speaker, and his twin brother, state Rep. Joaquin Castro, who is running for U.S. Congress, are interviewed at the Democratic National Convention in Charlotte, N.C., Monday, Sept. 3, 2012. less

San Antonio Mayor Julian Castro, left, who will be the convention keynote speaker, and his twin brother, state Rep. Joaquin Castro, who is running for U.S. Congress, are interviewed at the Democratic National ... more

Photo: Charles Dharapak, Associated Press

San Antonio Mayor Julian Castro, left, who will be the convention... Photo-3452439.48966 - StamfordAdvocate

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San Antonio Mayor Julian Castro, left, who will be the convention keynote speaker, and his twin brother, state Rep. Joaquin Castro, who is running for U.S. Congress, are interviewed at the Democratic National Convention in Charlotte, N.C., Monday, Sept. 3, 2012. less

San Antonio Mayor Julian Castro, left, who will be the convention keynote speaker, and his twin brother, state Rep. Joaquin Castro, who is running for U.S. Congress, are interviewed at the Democratic National ... more

Photo: Charles Dharapak, Associated Press

San Antonio Mayor Julian Castro, left, who will be the convention... Photo-3452440.48966 - StamfordAdvocate

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Mayoral candidate Julian Castro smiles after announcing his runoff election against Phil Hardberger at his campaign headquarters in the evening on Saturday, May 7, 2005. Castro was leading the early voting with 39 percent of the votes. less

Mayoral candidate Julian Castro smiles after announcing his runoff election against Phil Hardberger at his campaign headquarters in the evening on Saturday, May 7, 2005. Castro was leading the early voting with ... more

Councilman Julian Castro, center, candidate for San Antonio mayor, addresses the crowd Tuesday, June 7, 2005, in San Antonio at Castro's campaign headquarters. At left is his girlfriend, Erica Lira, and at right is his twin brother, Joaquin. Retired state judge Phil Hardberger held a narrow lead over Castro late Tuesday in the mayoral runoff. less

Councilman Julian Castro, center, candidate for San Antonio mayor, addresses the crowd Tuesday, June 7, 2005, in San Antonio at Castro's campaign headquarters. At left is his girlfriend, Erica Lira, and at ... more

San Antonio Mayor Julian Castro, left, and his brother, state Rep. Joaquin Castro give an interview during preparations for the Democratic National Convention at Time Warner Cable Arena on Sept. 3, 2012 in Charlotte, N.C. less

San Antonio Mayor Julian Castro, left, and his brother, state Rep. Joaquin Castro give an interview during preparations for the Democratic National Convention at Time Warner Cable Arena on Sept. 3, 2012 in ... more

Democrats view Julian Castro as a future star of the national party. Photo-3452457.48966 - StamfordAdvocate

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Mayor Castro is considered one of his party's best political orators.

Mayor Castro is considered one of his party's best political orators.

Mayor Castro is considered one of his party's best political... Photo-3452458.48966 - StamfordAdvocate

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Taboola Gallery Frame Item-85307.48966 - StamfordAdvocate

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Joaquin Castro left, introduces his twin brother and San Antonio Mayor Julian Castro during the the 2012 Texas Democratic Party State Convention at the George R. Brown Convention Center Friday, June 8, 2012, in Houston. less

Joaquin Castro left, introduces his twin brother and San Antonio Mayor Julian Castro during the the 2012 Texas Democratic Party State Convention at the George R. Brown Convention Center Friday, June 8, 2012, in ... more

Democratic Congressional Candidate Joaquin Castro speaks prior to introducing his twin brother and San Antonio Mayor Julian Castro during the the 2012 Texas Democratic Party State Convention at the George R. Brown Convention Center Friday, June 8, 2012, in Houston. less

Democratic Congressional Candidate Joaquin Castro speaks prior to introducing his twin brother and San Antonio Mayor Julian Castro during the the 2012 Texas Democratic Party State Convention at the George R. ... more